Artificial muscles comprising an electrode pair and artificial muscle assemblies including same

ABSTRACT

An artificial muscle that includes a housing having an electrode region and an expandable fluid region and an electrode pair positioned in the electrode region, the electrode pair having a first electrode fixed to a first surface of the housing and a second electrode fixed to a second surface of the housing. The first and second electrodes each have two or more tab portions and two or more bridge portions. Each of the two or more bridge portions interconnects adjacent tab portions and at least one of the first and second electrodes includes a central opening positioned between the two or more tab portions and encircling the expandable fluid region. A dielectric fluid is housed within the housing and the electrode pair is actuatable between a non-actuated and an actuated state such that actuation from the non-actuated to actuated state directs the dielectric fluid into the expandable fluid region.

TECHNICAL FIELD

The present specification generally relates to apparatus and methods for focused inflation on at least one surface of a device, and, more specifically, apparatus and methods for utilizing an electrode pair to direct a fluid to inflate the device.

BACKGROUND

Current robotic technologies rely on rigid components, such as servomotors to perform tasks, often in a structured environment. This rigidity presents limitations in many robotic applications, caused, at least in part, by the weight-to-power ratio of servomotors and other rigid robotics devices. The field of soft robotics improves on these limitations by using artificial muscles and other soft actuators. Artificial muscles attempt to mimic the versatility, performance, and reliability of a biological muscle. Some artificial muscles rely on fluidic actuators, but fluidic actuators require a supply of pressurized gas or liquid, and fluid transport must occur through systems of channels and tubes, limiting the speed and efficiency of the artificial muscles. Other artificial muscles use thermally activated polymer fibers, but these are difficult to control and operate at low efficiencies.

One particular artificial muscle design is described in the paper titled

Hydraulically amplified self-healing electrostatic actuators with muscle-like performance

by E. Acome, S. K. Mitchell, T. G. Morrissey, M. B. Emmett, C. Benjamin, M. King, M. Radakovitz, and C. Keplinger (Science 5 Jan. 2018: Vol. 359, Issue 6371, pp. 61-65). These hydraulically amplified self-healing electrostatic (HASEL) actuators use electrostatic and hydraulic forces to achieve a variety of actuation modes. However, HASEL actuator artificial muscles have a limited actuator power per unit volume.

Accordingly, a need exists for improved artificial muscles with increased actuator power per unit volume.

SUMMARY

In one embodiment, an artificial muscle includes a housing having an electrode region and an expandable fluid region and an electrode pair positioned in the electrode region of the housing, the electrode pair having a first electrode fixed to a first surface of the housing and a second electrode fixed to a second surface of the housing. The first electrode and the second electrode each have two or more tab portions and two or more bridge portions. Each of the two or more bridge portions interconnects adjacent tab portions and at least one of the first electrode and the second electrode includes a central opening positioned between the two or more tab portions and encircling the expandable fluid region. A dielectric fluid is housed within the housing and the electrode pair is actuatable between a non-actuated state and an actuated state such that actuation from the non-actuated state to the actuated state directs the dielectric fluid into the expandable fluid region.

In another embodiment, an artificial muscle assembly includes a plurality of artificial muscles, each artificial muscle having a housing with an electrode region and an expandable fluid region and an electrode pair positioned in the electrode region of the housing, the electrode pair including a first electrode fixed to a first surface of the housing and a second electrode fixed to a second surface of the housing. The first electrode and the second electrode each include two or more tab portions and two or more bridge portions. Each of the two or more bridge portions interconnects adjacent tab portions and at least one of the first electrode and the second electrode include a central opening positioned between the two or more tab portions and encircling the expandable fluid region. A dielectric fluid housed within the housing, the plurality of artificial muscles is arranged in a stack such that the expandable fluid region of each artificial muscle is coaxially aligned with one another, and the electrode pair is actuatable between a non-actuated state and an actuated state such that actuation from the non-actuated state to the actuated state directs the dielectric fluid into the expandable fluid region.

In yet another embodiment, a method for actuating an artificial muscle assembly includes generating a voltage using a power supply electrically coupled to an electrode pair of an artificial muscle, the artificial muscle having a housing with an electrode region and an expandable fluid region. The electrode pair is positioned in the electrode region of the housing. The electrode pair includes a first electrode fixed to a first surface of the housing and a second electrode fixed to opposing second surface of the housing. The first electrode and the second electrode each include two or more tab portions and two or more bridge portions. Each of the two or more bridge portions interconnects adjacent tab portions and at least one of the first electrode and the second electrode has a central opening positioned between the two or more tab portions encircling the expandable fluid region. A dielectric fluid is housed within the housing. The method further includes applying the voltage to the electrode pair of the artificial muscle, thereby actuating the electrode pair from a non-actuated state and an actuated state such that the dielectric fluid is directed into the expandable fluid region of the housing and expands the expandable fluid region.

These and additional features provided by the embodiments described herein will be more fully understood in view of the following detailed description, in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments set forth in the drawings are illustrative and exemplary in nature and not intended to limit the subject matter defined by the claims. The following detailed description of the illustrative embodiments can be understood when read in conjunction with the following drawings, where like structure is indicated with like reference numerals and in which:

FIG. 1 schematically depicts an exploded view of an illustrative artificial muscle, according to one or more embodiments shown and described herein;

FIG. 2 schematically depicts a top view of the artificial muscle of FIG. 1, according to one or more embodiments shown and described herein;

FIG. 3 schematically depicts a cross-sectional view of the artificial muscle of FIG. 1 taken along line 3-3 in FIG. 2 in a non-actuated state, according to one or more embodiments shown and described herein;

FIG. 4 schematically depicts a cross-sectional view of the artificial muscle of FIG. 3 in an actuated state, according to one or more embodiments shown and described herein;

FIG. 5 schematically depicts a cross-sectional view of an illustrative artificial muscle in a non-actuated state, according to one or more embodiments shown and described herein;

FIG. 6 schematically depicts a cross-sectional view of the artificial muscle of FIG. 5 in an actuated state, according to one or more embodiments shown and described herein;

FIG. 7 schematically depicts an artificial muscle assembly including a plurality of the artificial muscles of FIG. 1, according to one or more embodiments shown and described herein; and

FIG. 8 schematically depicts an actuation system for operating the artificial muscle of FIG. 1, according to one or more embodiments shown and described herein.

DETAILED DESCRIPTION

Embodiments described herein are directed to artificial muscles and artificial muscle assemblies that include a plurality of artificial muscles. The artificial muscles described herein are actuatable to selectively raise and lower a region of the artificial muscles to provide a selective, on demand inflated expandable fluid region. The artificial muscles include a housing and an electrode pair. A dielectric fluid is housed within the housing, and the housing includes an electrode region and an expandable fluid region, where the electrode pair is positioned in the electrode region. The electrode pair includes a first electrode fixed to a first surface of the housing and a second electrode fixed to a second surface of the housing. The electrode pair is actuatable between a non-actuated state and an actuated state such that actuation from the non-actuated state to the actuated state directs the dielectric fluid into the expandable fluid region. This expands the expandable fluid region, raising a portion of the artificial muscle on demand. Further, the first electrode and the second electrode each includes two or more tab portions and two or more bridge portions interconnecting adjacent tab portions, and at least one of the first electrode and the second electrode includes a central opening positioned between the tab portions and encircles the expandable fluid region. The tab portion and bridge portion design of the electrode pair facilitates a zippering actuation motion to increase the force per unit volume achievable by actuation of the artificial muscle. Various embodiments of the artificial muscle and the operation of the artificial muscle are described in more detail herein. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts.

Referring now to FIGS. 1 and 2, an artificial muscle 100 is shown. The artificial muscle 100 includes a housing 102, an electrode pair 104, including a first electrode 106 and a second electrode 108, fixed to opposite surfaces of the housing 102, a first electrical insulator layer 110 fixed to the first electrode 106, and a second electrical insulator layer 112 fixed to the second electrode 108. In some embodiments, the housing 102 is a one-piece monolithic layer including a pair of opposite inner surfaces, such as a first inner surface 114 and a second inner surface 116, and a pair of opposite outer surfaces, such as a first outer surface 118 and a second outer surface 120. In some embodiments, the first inner surface 114 and the second inner surface 116 of the housing 102 are heat-sealable. In other embodiments, the housing 102 may be a pair of individually fabricated film layers, such as a first film layer 122 and a second film layer 124. Thus, the first film layer 122 includes the first inner surface 114 and the first outer surface 118, and the second film layer 124 includes the second inner surface 116 and the second outer surface 120.

Throughout the ensuing description, reference may be made to the housing 102 including the first film layer 122 and the second film layer 124, as opposed to the one-piece housing. It should be understood that either arrangement is contemplated. In some embodiments, the first film layer 122 and the second film layer 124 generally include the same structure and composition. For example, in some embodiments, the first film layer 122 and the second film layer 124 each comprises biaxially oriented polypropylene.

The first electrode 106 and the second electrode 108 are each positioned between the first film layer 122 and the second film layer 124. In some embodiments, the first electrode 106 and the second electrode 108 are each aluminum-coated polyester such as, for example, Mylar®. In addition, one of the first electrode 106 and the second electrode 108 is a negatively charged electrode and the other of the first electrode 106 and the second electrode 108 is a positively charged electrode. For purposes discussed herein, either electrode 106, 108 may be positively charged so long as the other electrode 106, 108 of the artificial muscle 100 is negatively charged.

The first electrode 106 has a film-facing surface 126 and an opposite inner surface 128. The first electrode 106 is positioned against the first film layer 122, specifically, the first inner surface 114 of the first film layer 122. In addition, the first electrode 106 includes a first terminal 130 extending from the first electrode 106 past an edge of the first film layer 122 such that the first terminal 130 can be connected to a power supply to actuate the first electrode 106. Specifically, the terminal is coupled, either directly or in series, to a power supply and a controller of an actuation system 400, as shown in FIG. 8. Similarly, the second electrode 108 has a film-facing surface 148 and an opposite inner surface 150. The second electrode 108 is positioned against the second film layer 124, specifically, the second inner surface 116 of the second film layer 124. The second electrode 108 includes a second terminal 152 extending from the second electrode 108 past an edge of the second film layer 124 such that the second terminal 152 can be connected to a power supply and a controller of the actuation system 400 to actuate the second electrode 108.

The first electrode 106 includes two or more tab portions 132 and two or more bridge portions 140. Each bridge portion 140 is positioned between adjacent tab portions 132, interconnecting these adjacent tab portions 132. Each tab portion 132 has a first end 134 extending radially from a center axis C of the first electrode 106 to an opposite second end 136 of the tab portion 132, where the second end 136 defines a portion of an outer perimeter 138 of the first electrode 106. Each bridge portion 140 has a first end 142 extending radially from the center axis C of the first electrode 106 to an opposite second end 144 of the bridge portion 140 defining another portion of the outer perimeter 138 of the first electrode 106. Each tab portion 132 has a tab length L1 and each bridge portion 140 has a bridge length L2 extending in a radial direction from the center axis C of the first electrode 106. The tab length L1 is a distance from the first end 134 to the second end 136 of the tab portion 132 and the bridge length L2 is a distance from the first end 142 to the second end 144 of the bridge portion 140. The tab length L1 of each tab portion 132 is longer than the bridge length L2 of each bridge portion 140. In some embodiments, the bridge length L2 is 20% to 50% of the tab length L1, such as 30% to 40% of the tab length L1.

In some embodiments, the two or more tab portions 132 are arranged in one or more pairs of tab portions 132. Each pair of tab portions 132 includes two tab portions 132 arranged diametrically opposed to one another. In some embodiments, the first electrode 106 may include only two tab portions 132 positioned on opposite sides or ends of the first electrode 106. In some embodiments, as shown in FIGS. 1 and 2, the first electrode 106 includes four tab portions 132 and four bridge portions 140 interconnecting adjacent tab portions 132. In this embodiment, the four tab portion 132 are arranged as two pairs of tab portions 132 diametrically opposed to one another. Furthermore, as shown, the first terminal 130 extends from the second end 136 of one of the tab portions 132 and is integrally formed therewith.

Like the first electrode 106, the second electrode 108 includes at least a pair of tab portions 154 and two or more bridge portions 162. Each bridge portion 162 is positioned between adjacent tab portions 154, interconnecting these adjacent tab portions 154. Each tab portion 154 has a first end 156 extending radially from a center axis C of the second electrode 108 to an opposite second end 158 of the tab portion 154, where the second end 158 defines a portion of an outer perimeter 160 of the second electrode 108. Due to the first electrode 106 and the second electrode 108 being coaxial with one another, the center axis C of the first electrode 106 and the second electrode 108 are the same. Each bridge portion 162 has a first end 164 extending radially from the center axis C of the second electrode to an opposite second end 166 of the bridge portion 162 defining another portion of the outer perimeter 160 of the second electrode 108. Each tab portion 154 has a tab length L3 and each bridge portion 162 has a bridge length L4 extending in a radial direction from the center axis C of the second electrode 108. The tab length L3 is a distance from the first end 156 to the second end 158 of the tab portion 154 and the bridge length L4 is a distance from the first end 164 to the second end 166 of the bridge portion 162. The tab length L3 is longer than the bridge length L4 of each bridge portion 162. In some embodiments, the bridge length L4 is 20% to 50% of the tab length L3, such as 30% to 40% of the tab length L3.

In some embodiments, the two or more tab portions 154 are arranged in one or more pairs of tab portions 154. Each pair of tab portions 154 includes two tab portions 154 arranged diametrically opposed to one another. In some embodiments, the second electrode 108 may include only two tab portions 154 positioned on opposite sides or ends of the first electrode 106. In some embodiments, as shown in FIGS. 1 and 2, the second electrode 108 includes four tab portions 154 and four bridge portions 162 interconnecting adjacent tab portions 154. In this embodiment, the four tab portions 154 are arranged as two pairs of tab portions 154 diametrically opposed to one another. Furthermore, as shown, the second terminal 152 extends from the second end 158 of one of the tab portions 154 and is integrally formed therewith.

Referring now to FIGS. 1-6, at least one of the first electrode 106 and the second electrode 108 has a central opening formed therein between the first end 134 of the tab portions 132 and the first end 142 of the bridge portions 140. In FIGS. 3 and 4, the first electrode 106 has a central opening 146. However, it should be understood that the first electrode 106 does not need to include the central opening 146 when a central opening is provided within the second electrode 108, as shown in FIGS. 5 and 6. Alternatively, the second electrode 108 does not need to include the central opening when the central opening 146 is provided within the first electrode 106. Referring still to FIGS. 1-6, the first electrical insulator layer 110 and the second electrical insulator layer 112 have a geometry generally corresponding to the first electrode 106 and the second electrode 108, respectively. Thus, the first electrical insulator layer 110 and the second electrical insulator layer 112 each have tab portions 170, 172 and bridge portions 174, 176 corresponding to like portions on the first electrode 106 and the second electrode 108. Further, the first electrical insulator layer 110 and the second electrical insulator layer 112 each have an outer perimeter 178, 180 corresponding to the outer perimeter 138 of the first electrode 106 and the outer perimeter 160 of the second electrode 108, respectively, when positioned thereon.

It should be appreciated that, in some embodiments, the first electrical insulator layer 110 and the second electrical insulator layer 112 generally include the same structure and composition. As such, in some embodiments, the first electrical insulator layer 110 and the second electrical insulator layer 112 each include an adhesive surface 182, 184 and an opposite non-sealable surface 186, 188, respectively. Thus, in some embodiments, the first electrical insulator layer 110 and the second electrical insulator layer 112 are each a polymer tape adhered to the inner surface 128 of the first electrode 106 and the inner surface 150 of the second electrode 108, respectively.

Referring now to FIGS. 2-6, the artificial muscle 100 is shown in its assembled form with the first terminal 130 of the first electrode 106 and the second terminal 152 of the second electrode 108 extending past an outer perimeter of the housing 102, i.e., the first film layer 122 and the second film layer 124. As shown in FIG. 2, the second electrode 108 is stacked on top of the first electrode 106 and, therefore, the first electrode 106, the first film layer 122, and the second film layer 124 are not shown. In its assembled form, the first electrode 106, the second electrode 108, the first electrical insulator layer 110, and the second electrical insulator layer 112 are sandwiched between the first film layer 122 and the second film layer 124. The first film layer 122 is partially sealed to the second film layer 124 at an area surrounding the outer perimeter 138 of the first electrode 106 and the outer perimeter 160 of the second electrode 108. In some embodiments, the first film layer 122 is heat-sealed to the second film layer 124. Specifically, in some embodiments, the first film layer 122 is sealed to the second film layer 124 to define a sealed portion 190 surrounding the first electrode 106 and the second electrode 108. The first film layer 122 and the second film layer 124 may be sealed in any suitable manner, such as using an adhesive, heat sealing, or the like.

The first electrode 106, the second electrode 108, the first electrical insulator layer 110, and the second electrical insulator layer 112 provide a barrier that prevents the first film layer 122 from sealing to the second film layer 124 forming an unsealed portion 192. The unsealed portion 192 of the housing 102 includes an electrode region 194, in which the electrode pair 104 is provided, and an expandable fluid region 196, which is surrounded by the electrode region 194. The central openings 146, 168 of the first electrode 106 and the second electrode 108 form the expandable fluid region 196 and are arranged to be axially stacked on one another. Although not shown, the housing 102 may be cut to conform to the geometry of the electrode pair 104 and reduce the size of the artificial muscle 100, namely, the size of the sealed portion 190.

A dielectric fluid 198 is provided within the unsealed portion 192 and flows freely between the first electrode 106 and the second electrode 108. A

dielectric

fluid as used herein is a medium or material that transmits electrical force without conduction and as such has low electrical conductivity. Some non-limiting example dielectric fluids include perfluoroalkanes, transformer oils, and deionized water. It should be appreciated that the dielectric fluid 198 may be injected into the unsealed portion 192 of the artificial muscle 100 using a needle or other suitable injection device.

Referring now to FIGS. 3 and 4, the artificial muscle 100 is actuatable between a non-actuated state and an actuated state. In the non-actuated state, as shown in FIG. 3, the first electrode 106 and the second electrode 108 are partially spaced apart from one another proximate the central openings 146, 168 thereof and the first end 134, 156 of the tab portions 132, 154. The second end 136, 158 of the tab portions 132, 154 remain in position relative to one another due to the housing 102 being sealed at the outer perimeter 138 of the first electrode 106 and the outer perimeter 160 of the second electrode 108. In the actuated state, as shown in FIG. 4, the first electrode 106 and the second electrode 108 are brought into contact with and oriented parallel to one another to force the dielectric fluid 198 into the expandable fluid region 196. This causes the dielectric fluid 198 to flow through the central openings 146, 168 of the first electrode 106 and the second electrode 108 and inflate the expandable fluid region 196.

Referring now to FIG. 3, the artificial muscle 100 is shown in the non-actuated state. The electrode pair 104 is provided within the electrode region 194 of the unsealed portion 192 of the housing 102. The central opening 146 of the first electrode 106 and the central opening 168 of the second electrode 108 are coaxially aligned within the expandable fluid region 196. In the non-actuated state, the first electrode 106 and the second electrode 108 are partially spaced apart from and non-parallel to one another. Due to the first film layer 122 being sealed to the second film layer 124 around the electrode pair 104, the second end 136, 158 of the tab portions 132, 154 are brought into contact with one another. Thus, dielectric fluid 198 is provided between the first electrode 106 and the second electrode 108, thereby separating the first end 134, 156 of the tab portions 132, 154 proximate the expandable fluid region 196. Stated another way, a distance between the first end 134 of the tab portion 132 of the first electrode 106 and the first end 156 of the tab portion 154 of the second electrode 108 is greater than a distance between the second end 136 of the tab portion 132 of the first electrode 106 and the second end 158 of the tab portion 154 of the second electrode 108. This results in the electrode pair 104 zippering toward the expandable fluid region 196 when actuated. In some embodiments, the first electrode 106 and the second electrode 108 may be flexible. Thus, as shown in FIG. 3, the first electrode 106 and the second electrode 108 are convex such that the second ends 136, 158 of the tab portions 132, 154 thereof may remain close to one another, but spaced apart from one another proximate the central openings 146, 168. In the non-actuated state, the expandable fluid region 196 has a first height H1.

When actuated, as shown in FIG. 4, the first electrode 106 and the second electrode 108 zipper toward one another from the second ends 144, 158 of the tab portions 132, 154 thereof, thereby pushing the dielectric fluid 198 into the expandable fluid region 196. As shown, when in the actuated state, the first electrode 106 and the second electrode 108 are parallel to one another. In the actuated state, the dielectric fluid 198 flows into the expandable fluid region 196 to inflate the expandable fluid region 196. As such, the first film layer 122 and the second film layer 124 expand in opposite directions. In the actuated state, the expandable fluid region 196 has a second height H2, which is greater than the first height H1 of the expandable fluid region 196 when in the non-actuated state. Although not shown, it should be noted that the electrode pair 104 may be partially actuated to a position between the non-actuated state and the actuated state. This would allow for partial inflation of the expandable fluid region 196 and adjustments when necessary.

In order to move the first electrode 106 and the second electrode 108 toward one another, a voltage is applied by a power supply. In some embodiments, a voltage of up to 10 kV may be provided from the power supply to induce an electric field through the dielectric fluid 198. The resulting attraction between the first electrode 106 and the second electrode 108 pushes the dielectric fluid 198 into the expandable fluid region 196. Pressure from the dielectric fluid 198 within the expandable fluid region 196 causes the first film layer 122 and the first electrical insulator layer 110 to deform in a first axial direction along the center axis C of the first electrode 106 and causes the second film layer 124 and the second electrical insulator layer 112 to deform in an opposite second axial direction along the center axis C of the second electrode 108. Once the voltage being supplied to the first electrode 106 and the second electrode 108 is discontinued, the first electrode 106 and the second electrode 108 return to their initial, non-parallel position in the non-actuated state.

It should be appreciated that the present embodiments disclosed herein, specifically, the tab portions 132, 154 with the interconnecting bridge portions 174, 176, provide a number of improvements over actuators, such as HASEL actuators, that do not include the tab portions 132, 154. Embodiments of the artificial muscle 100 including two pairs of tab portions 132, 154 on each of the first electrode 106 and the second electrode 108, respectively, reduces the overall mass and thickness of the artificial muscle 100, reduces the amount of voltage required during actuation, and decreases the total volume of the artificial muscle 100 without reducing the amount of resulting force after actuation as compared to known HASEL actuators including donut-shaped electrodes having a uniform, radially-extending width. More particularly, the tab portions 132, 154 of the artificial muscle 100 provide zipping fronts that result in increased actuation power by providing localized and uniform hydraulic actuation of the artificial muscle 100 compared to HASEL actuators including donut-shaped electrodes. Specifically, one pair of tab portions 132, 154 provides twice the amount of actuator power per unit volume as compared to donut-shaped HASEL actuators, while two pairs of tab portions 132, 154 provide four times the amount of actuator power per unit volume. The bridge portions 174, 176 interconnecting the tab portions 132, 154 also limit buckling of the tab portions 132, 154 by maintaining the distance between adjacent tab portions 132, 154 during actuation. Because the bridge portions 174, 176 are integrally formed with the tab portions 132, 154, the bridge portions 174, 176 also prevent leakage between the tab portions 132, 154 by eliminating attachment locations that provide an increased risk of rupturing.

In operation, when the artificial muscle 100 is actuated, expansion of the expandable fluid region 196 produces a force of 3 Newton-millimeters (N mm) per cubic centimeter (cm³) of actuator volume or greater, such as 4 N·mm per cm³ or greater, 5 N mm per cm³ or greater, 6 N·mm per cm³ or greater, 7 N·mm per cm³ or greater, 8 N mm per cm³ or greater, or the like. In one example, when the artificial muscle 100 is actuated by a voltage of 9.5 kilovolts (kV), the artificial muscle 100 provides a resulting force of 5 N. In another example, when the artificial muscle 100 is actuated by a voltage of 10 kV the artificial muscle 100 provides 440% strain under a 500 gram load.

Moreover, the size of the first electrode 106 and the second electrode 108 is proportional to the amount of displacement of the dielectric fluid 198. Therefore, when greater displacement within the expandable fluid region 196 is desired, the size of the electrode pair 104 is increased relative to the size of the expandable fluid region 196. It should be appreciated that the size of the expandable fluid region 196 is defined by the central openings 146, 168 in the first electrode 106 and the second electrode 108. Thus, the degree of displacement within the expandable fluid region 196 may alternatively, or in addition, be controlled by increasing or reducing the size of the central openings 146, 168.

As shown in FIGS. 5 and 6, another embodiment of an artificial muscle 200 is illustrated. The artificial muscle 200 is substantially similar to the artificial muscle 100. As such, like structure is indicated with like reference numerals. However, as shown, the first electrode 106 does not include a central opening. Thus, only the second electrode 108 includes the central opening 168 formed therein. As shown in FIG. 5, the artificial muscle 200 is in the non-actuated state with the first electrode 106 being planar and the second electrode 108 being convex relative to the first electrode 106. In the non-actuated state, the expandable fluid region 196 has a first height H3. In the actuated state, as shown in FIG. 6, the expandable fluid region 196 has a second height H4, which is greater than the first height H3. It should be appreciated that by providing the central opening 168 only in the second electrode 108 as opposed to both the first electrode 106 and the second electrode 108, the total deformation may be formed on one side of the artificial muscle 200. In addition, because the total deformation is formed on only one side of the artificial muscle 200, the second height H4 of the expandable fluid region 196 of the artificial muscle 200 extends further from a longitudinal axis perpendicular to the central axis C of the artificial muscle 200 than the second height H2 of the expandable fluid region 196 of the artificial muscle 100 when all other dimensions, orientations, and volume of dielectric fluid are the same.

Referring now to FIG. 7, an artificial muscle assembly 300 is shown including a plurality of artificial muscles, such the artificial muscle 100. However, it should be appreciated that a plurality of artificial muscles 200 may similarly be arranged in a stacked formation. Each artificial muscle 100 may be identical in structure and arranged in a stack such that the expandable fluid region 196 of each artificial muscle 100 overlies the expandable fluid region 196 of an adjacent artificial muscle 100. The terminals 130, 152 of each artificial muscle 100 are electrically connected to one another such that the artificial muscles 100 may be simultaneously actuated between the non-actuated state and the actuated state. By arranging the artificial muscles 100 in a stacked configuration, the total deformation of the artificial muscle assembly 300 is the sum of the deformation within the expandable fluid region 196 of each artificial muscle 100. As such, the resulting degree of deformation from the artificial muscle assembly 300 is greater than that which would be provided by the artificial muscle 100 alone.

Referring now to FIG. 8, an actuation system 400 may be provided for operating an artificial muscle or an artificial muscle assembly, such as the artificial muscles 100, 200 or the artificial muscle assembly 300 between the non-actuated state and the actuated state. Thus, the actuation system 400 may include a controller 402, an operating device 404, a power supply 406, and a communication path 408. The various components of the actuation system 400 will now be described.

The controller 402 includes a processor 410 and a non-transitory electronic memory 412 to which various components are communicatively coupled. In some embodiments, the processor 410 and the non-transitory electronic memory 412 and/or the other components are included within a single device. In other embodiments, the processor 410 and the non-transitory electronic memory 412 and/or the other components may be distributed among multiple devices that are communicatively coupled. The controller 402 includes non-transitory electronic memory 412 that stores a set of machine-readable instructions. The processor 410 executes the machine-readable instructions stored in the non-transitory electronic memory 412. The non-transitory electronic memory 412 may comprise RAM, ROM, flash memories, hard drives, or any device capable of storing machine-readable instructions such that the machine-readable instructions can be accessed by the processor 410. Accordingly, the actuation system 400 described herein may be implemented in any conventional computer programming language, as pre-programmed hardware elements, or as a combination of hardware and software components. The non-transitory electronic memory 412 may be implemented as one memory module or a plurality of memory modules.

In some embodiments, the non-transitory electronic memory 412 includes instructions for executing the functions of the actuation system 400. The instructions may include instructions for operating the artificial muscles 100, 200 or the artificial muscle assembly 300 based on a user command.

The processor 410 may be any device capable of executing machine-readable instructions. For example, the processor 410 may be an integrated circuit, a microchip, a computer, or any other computing device. The non-transitory electronic memory 412 and the processor 410 are coupled to the communication path 408 that provides signal interconnectivity between various components and/or modules of the actuation system 400. Accordingly, the communication path 408 may communicatively couple any number of processors with one another, and allow the modules coupled to the communication path 408 to operate in a distributed computing environment. Specifically, each of the modules may operate as a node that may send and/or receive data. As used herein, the term U communicatively couple& means that coupled components are capable of exchanging data signals with one another such as, for example, electrical signals via conductive medium, electromagnetic signals via air, optical signals via optical waveguides, and the like.

As schematically depicted in FIG. 8, the communication path 408 communicatively couples the processor 410 and the non-transitory electronic memory 412 of the controller 402 with a plurality of other components of the actuation system 400. For example, the actuation system 400 depicted in FIG. 8 includes the processor 410 and the non-transitory electronic memory 412 communicatively coupled with the operating device 404 and the power supply 406.

The operating device 404 allows for a user to control operation of the artificial muscles 100, 200 or the artificial muscle assembly 300. In some embodiments, the operating device 404 may be a switch, toggle, button, or any combination of controls to provide user operation. As a non-limiting example, a user may actuate the artificial muscles 100, 200 or the artificial muscle assembly 300 into the actuated state by activating controls of the operating device 404 to a first position. While in the first position, the artificial muscles 100, 200 or the artificial muscle assembly 300 will remain in the actuated state. The user may switch the artificial muscles 100, 200 or the artificial muscle assembly 300 into the non-actuated state by operating the controls of the operating device 404 out of the first position and into a second position.

The operating device 404 is coupled to the communication path 408 such that the communication path 408 communicatively couples the operating device 404 to other modules of the actuation system 400. The operating device 404 may provide a user interface for receiving user instructions as to a specific operating configuration of the artificial muscles 100, 200 or the artificial muscle assembly 300. In addition, user instructions may include instructions to operate the artificial muscles 100, 200 or the artificial muscle assembly 300 only at certain conditions.

The power supply 406 (e.g., battery) provides power to the artificial muscles 100, 200 or the artificial muscle assembly 300. In some embodiments, the power supply 406 is a rechargeable direct current power source. It is to be understood that the power supply 406 may be a single power supply or battery for providing power to the artificial muscle 100, 200 or the artificial muscle assembly 300. A power adapter (not shown) may be provided and electrically coupled via a wiring harness or the like for providing power to the artificial muscles 100, 200 or the artificial muscle assembly 300 via the power supply 406.

In some embodiments, the actuation system 400 also includes a display device 414. The display device 414 is coupled to the communication path 408 such that the communication path 408 communicatively couples the display device 414 to other modules of the actuation system 400. The display device 414 may output a notification in response to an actuation state of the artificial muscles 100, 200 or the artificial muscle assembly 300 or indication of a change in the actuation state of the artificial muscles 100, 200 or the artificial muscle assembly 300. Moreover, the display device 414 may be a touchscreen that, in addition to providing optical information, detects the presence and location of a tactile input upon a surface of or adjacent to the display device 414. Accordingly, the display device 414 may include the operating device 404 and receive mechanical input directly upon the optical output provided by the display device 414.

In some embodiments, the actuation system 400 includes network interface hardware 416 for communicatively coupling the actuation system 400 to a portable device 418 via a network 420. The portable device 418 may include, without limitation, a smartphone, a tablet, a personal media player, or any other electric device that includes wireless communication functionality. It is to be appreciated that, when provided, the portable device 418 may serve to provide user commands to the controller 402, instead of the operating device 404. As such, a user may be able to control or set a program for controlling the artificial muscles 100, 200 or the artificial muscle assembly 300 without utilizing the controls of the operating device 404. Thus, the artificial muscles 100, 200 or the artificial muscle assembly 300 may be controlled remotely via the portable device 418 wirelessly communicating with the controller 402 via the network 420.

From the above, it is to be appreciated that defined herein is an artificial muscle for inflating or deforming a surface of an object by selectively actuating the artificial muscle to raise and lower a region thereof. This provides a low profile inflation member that may operate on demand.

It is noted that the terms “substantially” and “about” may be utilized herein to represent the inherent degree of uncertainty that may be attributed to any quantitative comparison, value, measurement, or other representation. These terms are also utilized herein to represent the degree by which a quantitative representation may vary from a stated reference without resulting in a change in the basic function of the subject matter at issue.

While particular embodiments have been illustrated and described herein, it should be understood that various other changes and modifications may be made without departing from the scope of the claimed subject matter. Moreover, although various aspects of the claimed subject matter have been described herein, such aspects need not be utilized in combination. It is therefore intended that the appended claims cover all such changes and modifications that are within the scope of the claimed subject matter. 

What is claimed is:
 1. An artificial muscle comprising: a housing comprising an electrode region and an expandable fluid region; an electrode pair positioned in the electrode region of the housing, the electrode pair comprising a first electrode fixed to a first surface of the housing and a second electrode fixed to a second surface of the housing, wherein: the first electrode and the second electrode each comprise two or more tab portions and two or more bridge portions, wherein: each of the two or more bridge portions interconnects adjacent tab portions; and at least one of the first electrode and the second electrode comprises a central opening positioned between the two or more tab portions and encircling the expandable fluid region; and a dielectric fluid housed within the housing; wherein the electrode pair is actuatable between a non-actuated state and an actuated state such that actuation from the non-actuated state to the actuated state directs the dielectric fluid into the expandable fluid region.
 2. The artificial muscle of claim 1, wherein the housing comprises a first film layer and a second film layer partially sealed to one another to define a sealed portion of the housing, the housing further comprising an unsealed portion surrounded by the sealed portion, wherein the electrode region and the expandable fluid region of the housing are disposed in the unsealed portion.
 3. The artificial muscle of claim 2, wherein the first film layer and the second film layer are each biaxially oriented polypropylene films.
 4. The artificial muscle of claim 1, further comprising a first electrical insulator layer fixed to an inner surface of the first electrode opposite the first surface of the housing and a second electrical insulator layer fixed to an inner surface of the second electrode opposite the second surface of the housing, wherein the first electrical insulator layer and the second electrical insulator layer each includes an adhesive surface and an opposite non-sealable surface.
 5. The artificial muscle of claim 1, wherein the first electrode and the second electrode are each an aluminum-coated polyester electrode.
 6. The artificial muscle of claim 1, wherein the first electrode and the second electrode each includes two pairs of tab portions and two pairs of bridge portions, each bridge portion interconnecting adjacent a pair of adjacent tab portions, each tab portion diametrically opposing an opposite tab portion.
 7. The artificial muscle of claim 1, wherein the two or more tab portions each have a tab length and the two or more bridge portions each have a bridge length extending radially from the central opening, the bridge length being 20% to 50% of the tab length.
 8. The artificial muscle of claim 1, wherein each of the first electrode and the second electrode comprise a central opening positioned between the two or more tab portions and encircling the expandable fluid region, the central openings being coaxially aligned with one another.
 9. The artificial muscle of claim 1, wherein: when the electrode pair is in the non-actuated state, the first electrode and the second electrode are non-parallel to one another; and when the electrode pair is in the actuated state, the first electrode and the second electrode are parallel to one another, such that the first electrode and the second electrode are configured to zipper toward one another and toward the central opening when actuated from the non-actuated state to the actuated state.
 10. An artificial muscle assembly comprising: a plurality of artificial muscles, each artificial muscle comprising: a housing comprising an electrode region and an expandable fluid region; an electrode pair positioned in the electrode region of the housing, the electrode pair comprising a first electrode fixed to a first surface of the housing and a second electrode fixed to a second surface of the housing, wherein: the first electrode and the second electrode each comprise two or more tab portions and two or more bridge portions, wherein: each of the two or more bridge portions interconnects adjacent tab portions; and at least one of the first electrode and the second electrode comprise a central opening positioned between the two or more tab portions and encircling the expandable fluid region; and a dielectric fluid housed within the housing, wherein the plurality of artificial muscles is arranged in a stack such that the expandable fluid region of each artificial muscle is coaxially aligned with one another; and wherein the electrode pair is actuatable between a non-actuated state and an actuated state such that actuation from the non-actuated state to the actuated state directs the dielectric fluid into the expandable fluid region.
 11. The artificial muscle assembly of claim 10, wherein the plurality of artificial muscles are electrically coupled to one another and configured to simultaneously actuate between the non-actuated state and the actuated state.
 12. The artificial muscle assembly of claim 10, further comprising: a first electrical insulator layer fixed to an inner surface of the first electrode opposite the first surface of the housing and a second electrical insulator layer fixed to an inner surface of the second electrode opposite the second surface of the housing, wherein the first electrical insulator layer and the second electrical insulator layer each includes an adhesive surface and an opposite non-sealable surface.
 13. The artificial muscle of claim 10, wherein the first electrode and the second electrode each includes two pairs of tab portions and two pairs of bridge portions, each bridge portion interconnecting a pair of adjacent tab portions, each tab portion diametrically opposing an opposite tab portion.
 14. The artificial muscle of claim 10, wherein each of the first electrode and the second electrode comprise a central opening positioned between the two or more tab portions and encircling the expandable fluid region, the central openings being coaxially aligned with one another.
 15. The artificial muscle of claim 10, wherein: when the electrode pair is in the non-actuated state, the first electrode and the second electrode are non-parallel to one another; and when the electrode pair is in the actuated state, the first electrode and the second electrode are parallel to one another, such that the first electrode and the second electrode are configured to zipper toward one another and toward the central opening when actuated from the non-actuated state to the actuated state.
 16. A method for actuating an artificial muscle assembly, the method comprising: generating a voltage using a power supply electrically coupled to an electrode pair of an artificial muscle, the artificial muscle comprising a housing with an electrode region and an expandable fluid region, wherein: the electrode pair is positioned in the electrode region of the housing; the electrode pair comprises a first electrode fixed to a first surface of the housing and a second electrode fixed to opposing second surface of the housing; the first electrode and the second electrode each comprise two or more tab portions and two or more bridge portions, wherein: each of the two or more bridge portions interconnects adjacent tab portions; and at least one of the first electrode and the second electrode comprises a central opening positioned between the two or more tab portions encircling the expandable fluid region; and a dielectric fluid is housed within the housing, and applying the voltage to the electrode pair of the artificial muscle, thereby actuating the electrode pair from a non-actuated state and an actuated state such that the dielectric fluid is directed into the expandable fluid region of the housing and expands the expandable fluid region.
 17. The method of claim 16, wherein the housing comprises a first film layer and a second film layer, and partially heat sealing the first film layer and the second to one another to define a sealed portion of the housing, the housing further comprising an unsealed portion surrounded by the sealed portion, wherein the electrode region and the expandable fluid region of the housing are disposed in the unsealed portion.
 18. The method of claim 16, wherein a controller is communicatively coupled to the electrode pair, and the controller directing a voltage from the power supply across the first electrode and the second electrode to actuate the artificial muscle from the non-actuated state to the actuated state.
 19. The method of claim 16, wherein the artificial muscle is one of a plurality of artificial muscles arranged in a stack such that the expandable fluid region of each artificial muscle is coaxially aligned with one another.
 20. The method of claim 16, wherein expanding the expandable fluid region produces a force greater than 4 N·mm per cm³ of actuator volume. 